The Importance of Upwelling

 

Upwelling: many of you may have heard of it, and many of you may have no idea what it is. Regardless of what you may know, upwelling is extremely important in creating and sustaining life within all oceans. It is so important that, if missing, we might not be around much longer either.

Upwelling is the process where cool water is brought up from the depths of the ocean, full of delicious nutrients ready for consumption by tiny phytoplankton. This cool water replaces the warm, barren and ‘stale’ water that sits at the surface layer, giving the phytoplankton the food they need to produce the energy that is then bestowed upon the rest of the marine food web. Phytoplankton sit in the water and suck up all the nutrients surrounding them, which they then use to power growth.

A nudibranch off Blairgowrie pier: one of the many creatures within Port Phillip Bay that benefits from upwelling in Bass Strait.

A nudibranch off Blairgowrie pier: one of the many creatures within Port Phillip Bay that benefits from upwelling in Bass Strait.

Phytoplankton fill the niche space (a ‘sciencey’ word for a position in the food web) of a plant, as they are primary producers. Primary producers use sunlight to create energy using photosynthesis, as well as utilising the nutrients brought up from the depths of the ocean to move this energy up the food chain, allowing life to bloom. Phytoplankton therefore sequester the nutrients and convert sunlight into energy, and are in turn eaten by zooplankton, which are then eaten by larger and larger organisms, eventually reaching the apex predators, such as killer whales, dolphins and, my favorite, SHARKS! This process of nutrient acquirement makes up something you might have heard of before: the food chain!

If that description confuses you a little or doesn’t seem clear, we can use the analogy of a plant. Imagine any plant that has roots in the soil: the roots sit in the soil so that the plant can access the nutrients found there. Each root pulls in nutrients essential for life processes, such as phosphorus, nitrogen and potassium. These nutrients are then used to power the plant. Primary consumers then eat these plants, moving the nutrients up the food chain. Predators then chase these consumers and subsequently eat them, thus moving the nutrients up to the apex of the food chain.

In a nutshell, if you can’t get your nutrients, you can’t exist. For example, carbon is used in the construction of a plant by forming the backbone of most essential biomolecules, such as cellulose and starches. As many of you may already know from basic chemistry, carbon is pretty much the most essential element on earth, as it allows life to exist!

Now back to upwelling and why it is so important. Upwelling doesn’t occur all the time, as in the terrestrial environment there are seasons when not much food is available, and other times when there is. For Victoria in particular, the greatest period of upwelling is springtime. That’s right - NOW!

As a result of this huge upwelling, we see large marine animals visiting our coasts. Most would be aware that we have recently had humpback whales passing through our waters. You might be surprised to know that we also have the largest animal in the world moving into our waters during this period: the blue whale! It is amazing to think that microscopic phytoplankton can bring the biggest animal in the world to Australia’s own shores. Such an event truly draws attention to how influential these little critters are in the oceans of the world. It is even more amazing that something so small and (almost) invisible can be so integral to keeping the oceans afloat.

Australasian Gannets hanging out at Pope’s Eye. These are among the many seabirds that benefit from the upwelling in Bass Strait.


Australasian Gannets hanging out at Pope’s Eye. These are among the many seabirds that benefit from the upwelling in Bass Strait.

 

So even though all the nature we can see with our eyes is both beautiful and vital when it comes to the survival of life, it’s the things that we maybe can’t see directly that are even more important. If you wish to witness the changes that upwelling can bring to the marine environment, jump in the water somewhere during the middle of winter, and you’ll find that it’s pretty quiet. Then go and have another look around early summer, sometime near Christmas, and experience the change in activity - you will be amazed!